1. Field of the Invention
This invention relates to a light or heat output stabilizing system for stabilizing the light output of a light source or the heat output of a heat source in a light or heat beam scanning and recording apparatus for recording an image by scanning a scanning surface with a light beam emitted from the light source or a heat beam emitted from the heat source. This invention particularly relates to a light or heat output stabilizing system for stabilizing the light output of a light source such as a semiconductor laser or a light emitting diode or the heat output of a heat source such as a semiconductor laser or a light emitting diode in a recording apparatus which has at least one light source or at least one heat source mounted on a rotating body and which simultaneously carries out both modulation and deflection of the light beam emitted from the light source or the heat beam emitted from the heat source while the light source or the heat source is rotated together with the rotating body.
2. Description of the Prior Art
Laser beam sources can generate light beams exhibiting high spatial interference and a high spectral line brightness that cannot be obtained with the other types of light sources. Because of these advantages, laser beam sources are used for many optical read out and recording apparatuses. For example, the laser beam sources are used for read-out apparatuses such as in facsimile transmitters, automatic readers for label bar codes, and film flaw detectors. Laser beam sources are also used for recording apparatuses such as in video disc recorders and facsimile receivers. In the past, these laser-based apparatuses mainly employed gas lasers such as He-Ne, He-Cd and Ar lasers. However, gas laser beam sources are intrinsically large in size and, in addition, necessitate additional light scanners and light modulators for deflecting and modulating the light beam during scanning with the light beam. Consequently, such apparatuses using gas lasers are, in general, large in size and expensive. Thus, recently, semiconductor laser apparatuses which are small and exhibit high efficiency have come into increasingly wide use. One example of such an apparatus is that disclosed in Japanese Unexamined Patent Publication No. 57(1982)-151933 in which a semiconductor laser beam source is rotated to form linear scanning lines.
The optical rotational printer described in Japanese Unexamined Patent Publication No. 57(1982)-151933 is small in size and inexpensive, and yet can modulate and deflect the light beam without necessitating additional devices. However, this apparatus is disadvantageous in that, since the light output intensity of the semiconductor laser is markedly dependent on temperature, image nonuniformity readily arises on a recording material scanned with the laser beam emitted from the semiconductor laser when the ambient temperature fluctuates.
In order to eliminate the aforesaid drawback, it is necessary to stabilize the light output of the semiconductor laser. One approach to this is to directly control the temperature of the semiconductor laser. However, this method is not suitable since it complicates the mounting of the semiconductor laser and is difficult to implement because the space in the rotating body is limited.
On the other hand, in a system using a semiconductor laser for optical communication, a method wherein the light output is stabilized by controlling the bias current for superposition of a modulating signal is generally used. However, it is impossible to apply such a method to an apparatus for image recording including a DC component.